The purpose of this research study is to learn more about how activation of blood cells (T-cells and monocytes) induces human cytomegalovirus (HCMV) replication. HCMV infects over 50% of the U.S. population generally without causing disease. However, in immunosuppressed individuals (transplant and AIDS patients) the virus causes lethal disease. This study is investigating the mechanisms of how the HCMV is activated in blood cells which are a major reservoir of virus. Participants' blood cells will be used for laboratory infection with HCMV to analyze viral replication.